The natural 6. Re1 is in fact a very minor sideline; not only does it commit the rook to the e-file unnecessarily, but it allows Black's knight to retreat to c5, forcing the exchange of the a4-bishop. If Bxc6 dxc6, Black is then doing rather well compared to the Exchange Variation as the bishop has lost a tempo and the disappearance of the centre pawns favours Black's bishop pair.

The immediate attempt to grab the pawn back with 6. Bxc6 and 7. Nxe5 is similar but even kinder to Black; it gives her a knight on e5 to gang up on.

Instead, White should control c5 with 6. d4 which tends to be a good developing move anyway. This threatens Black's e-pawn again, while the complications resulting from 6...exd4 are not considered too much to handle.